A bit line sense amplifier is structured by a PMOS sense amplifier and a NMOS sense amplifier. The bit line sense amplifier amplifies data loaded in a bit line and a bit bar line of a semiconductor memory device, and thereby outputting thereof through an IO line.
In IO lines between the PMOS sense amplifier and the NMOS sense amplifier, and a layout structure of a bit line sense amplifier where an IO switch is arranged to connect the bit line and a bit bar line, a distance difference from a drain of the IO switch to each gate of a NMOS sense amplifier sharing the drain of the IO switch, a bit line and the bit bar line changes a loading of the bit line and the bit bar line. Also, a distance difference to each gate of a PMOS sense amplifier changes the loading of the bit line and the bit bar line. If the loading of the bit line is different from that of the bit bar line, there is a disadvantage to deteriorate characteristic of a memory core due to a develop difference between the bit line and the bit bar line when the IO switch is turned on.